The present invention relates generally to seats for crew members of vehicles such as locomotives and more particularly to seats of this type which are vertically adjustable and rotatable.
A conventional crew seat comprises an assembly including a seat cushion attached atop a vertically disposed trunnion member received within a vertically disposed tubular intermediate member in turn supported by a vertically disposed tubular base member which rests on the floor of the vehicle or is cantilevered from a side of the vehicle. Usually, the trunnion member is mounted for rotation about its vertical axis, relative to the tubular intermediate member, and the tubular intermediate member is mounted for vertical adjustment, with the trunnion member, relative to the base member. The seat cushion moves with the trunnion member.
The tubular intermediate member has an upper portion terminating at a top edge defining an open upper end. The trunnion member has a lower portion received within the upper portion of the tubular intermediate member and an upper peripheral lip portion radially overlapping the top edge of the tubular intermediate member. The upper peripheral lip portion of the trunnion member has a lower surface engaging against the top edge of the upper portion of the tubular intermediate member, and when the seat is rotated about the vertical axis of the trunnion member, there is wear between the lower surface on the upper peripheral lip portion of the trunnion member and the top edge on the upper portion of the tubular intermediate member.
It is desirable to be able to lock the seat in one or more predetermined positions of rotation, and this is accomplished by employing a hole extending radially inwardly in the lower portion of the trunnion member. This hole may be rotated into radial alignment with one of a plurality of peripherally or circumferentially spaced holes in the upper portion of the tubular intermediate member, and a pin may be inserted through the radially aligned openings to lock the seat in the position of rotation defined by the aligned openings. The hole in the lower portion of the trunnion member and the circumferentially spaced holes in the upper portion of the tubular intermediate member are located at the same vertical level. However, as a result of the wear described in the preceding paragraph, there can be a drop in the vertical level of the hole in the lower portion of the trunnion member, relative to the vertical level of the holes in the upper portion of the tubular intermediate member. When this occurs, the pin cannot be inserted through both a hole in the upper portion of the tubular intermediate member and the hole in the lower portion of the trunnion member, and the seat cannot be locked in a predetermined position of rotation.
A seat employing conventional mounting structure of the type described above is shown in Buker U.S. Pat. No. 3,960,406.